SAW Metallization Study

SAW metallization presents the designer with a great deal of variables. OnScale can be used to clearly present the design trade offs which exist, allowing the optimum design to be reached quickly.

In this example we vary both the aspect ratio of the SAW electrode fingers and the thickness of the electrode layer itself.

Model Setup

A schematic of the model and the two input variables can be seen below:

The key model parameters were as follows. Electrode thickness and electrode aspect ratio are set as design variables to be swept (indicated by *)

Design Variable

Description

Default Value

elec_thk *

Thickness of electrode

200 nm

subs_thk

Thickness of substrate

7.5 µm

fin_pitch

Finger pitch

1.3 µm

aratio *

Metalization aspect ratio

0.5

nfing

Number of pairs of fingers in full device

100

fin_len

Length of fingers

50 µm

piezo_mat

Piezoelectric material

lt (LiTaO3)

cut_ang

Rotated y-cut angle

0.5

Input variables were swept as follows:

Aspect ratio: 0.4 – 0.6 (10 steps)

Electrode thk: 180 – 220 nm (10 steps)

Simulation Sweep Results

The full simulation sweep was completed in 3 minutes when using 8 cores per simulation and had a total cost of 40 core hours.

Using the outputs from the simulations, it is possible to calculate the device impedance, Q factor and resonant frequencies. These outputs can all be plotted against the input variables to provide an insight into the device performance. Results are plotted below.